1. Field of the Invention
The present invention relates to a method and a device for engraving a semiconductor wafer identification mark, which includes inspecting the engraving state of the identification mark engraved by a laser beam on the surface of a semiconductor wafer in the manufacturing process of the wafer, and controlling the engraving by the engraving device in accordance with the inspection.
2. Description of the Related Art
Conventionally, in the manufacturing process of a semiconductor wafer, a semiconductor wafer with an identification mark such as a character or a barcode engraved on the surface thereof by a laser beam is manufactured by the following process:
(1) cutting an ingot to obtain a sliced wafer;
(2) engraving an identification mark on the surface of the sliced wafer by use of an engraving device;
(3) lapping the sliced wafer;
(4) etching the lapped wafer;
(5) polishing and washing the etched wafer; and
(6) drying the washed wafer and reading only the barcode of the mark to inspect.
In this manufacturing process, inspection of nonconformities such as mispositioning of the engraved mark, stains or deflection of the characters is performed through each of the following processes:
(a) extracting one wafer immediately after the engraving of the identification mark by the engraving device, printing out the image by use of an identification mark-reading device, and inspecting the characters or the barcodes of the mark visually; and
(b) if the etching solution used in the etching reacts with the engraving scraps produced in the engraving, in order to confirm the stain, performing the barcode reading step for all the wafers immediately after the etching;
(c) after the final manufacturing process of the semiconductor wafer is completed, inspecting all the wafers by reading the barcode.
However, inspecting the image visually immediately after the engraving of the identification mark can only be performed at a frequency of 1 piece for 100 pieces of the manufactured semiconductor wafers in view of the manufacturing efficiency. It is difficult to inspect all the manufactured semiconductor wafers by this conventional method.
Moreover, even if defective marks are found in the barcode-reading inspection which is performed immediately after the etching or the final manufacturing process and if the defective marks are caused by the identification mark-engraving device, a large amount of defective items is produced. This results in a waste of time and money up through the finish of the etching process or the final manufacturing process.
Moreover, the barcode-reading inspection does not inspect the characters themselves, and thus even if the character of the identification mark of the semiconductor wafers not taken out in the image inspection is defective, the semiconductor wafer bearing the defective mark will be delivered to the market.
In view of the above problems, an object of the invention is to provide an engraving device for engraving an identification mark on a semiconductor wafer, which inspects all the engraved marks, as well as an engraving method using the engraving device, which can prevent the engraving of defective marks.
In accordance with the invention, the method for engraving an identification mark on a semiconductor wafer includes measuring the thickness of a sliced wafer, inputting the thickness information into an engraving device, inputting the engraving information of the mark to be engraved into the engraving device, deciding the shape of the mark and the engraving depth from the thickness information and the engraving information, engraving the mark on the sliced wafer, obtaining the read information of the engraved mark, comparing the read information with the engraving information, and controlling the engraving by the engraving device in accordance with the results.
Moreover, the device for engraving a semiconductor wafer identification mark includes a turntable supporting the bottom surface of a semiconductor wafer for rotating the semiconductor wafer in the horizontal direction, an engraving device body for inputting the engraving information of the engraved mark, a laser head disposed at the upper portion of the semiconductor wafer supported on the turntable and connected to the engraving device body, a reading body device for reading the engraved mark, a reading camera disposed at the upper portion of the semiconductor wafer supported on the turntable and connected to the reading device body, an information processing device for comparing the reading information of the mark with the engraved information. The engraving is controlled by the engraving device body in accordance with the comparison result.
The invention concerns to an engraving device which can simultaneously perform the engraving of the mark on the semiconductor wafer and the inspection of all the semiconductor wafers and control the device by comparing the results of the engraving and the inspection; as well as an engraving method which can prevent the recurrence of the defective mark in the control of the engraving device when a defective mark is engraved.